When a search and rescue operation is required, as for a downed airplane or helicopter pilot for example, search and rescue radio (SAR) system interrogators are typically employed. Such search and rescue radio systems include a small portable radio which is in the possession of the downed pilot. Such systems may further include an interrogation unit which is typically carried in the rescue aircraft (helicopter or plane).
Important information required by the search and rescue aircraft includes correct identity of the survival radio. Identification is important to avoid, for example, decoy signals or traps by hostile forces. Other important information is the location of the radio and associated downed pilot.
The Global Positioning System (GPS) is particularly useful for determining position. Survival radios have been known to have GPS receivers capable of self determination of position.
Search and rescue interrogation units typically include a GPS receiver, portable computer and a separate transceiver. Communication between interrogation units and survival radios is linked to Line of Sight (LOS) communication links. However, in many cases, it would be desirable to extend the LOS communication link to communication links that could extend over the horizon (OTH).